As it is known, occasionally wind turbines connected to the electricity network cannot inject all the electric energy produced to said electricity network due to technical or legal limitations. Therefore, for the purpose of profitably using the energy that is being produced, one of the uses thereof is the generation of hydrogen by means of an electrolyzer, in order to subsequently use the hydrogen produced and stored in different ways.
One of the uses can be the distribution of hydrogen to the hydrogen distribution stations, for use thereof as a fuel in vehicles or the selling of hydrogen itself.
Likewise, another possible use is the utilization of said hydrogen to produce electricity and inject it again into the electricity network.
There are numerous publications that set forth systems that integrate the generation of renewable energy and hydrogen.
As to the production of electricity with hydrogen coming from wind energy, there are patent applications such as: WO2006097494 and EP1596052, that propose generating hydrogen by electrolysis, that would be later used to produce energy by conventional gas or steam plants.
Furthermore, DE10055973 describes a system for producing and storing hydrogen with wind energy, for the purpose of using it to produce electricity and inject it in the wind turbine power outlet, in order to adjust the power output of the wind farm.
Finally, there are publications, such as U.S. Pat. No. 7,199,482 that describes the regulation of power of a wind farm by means of increasing or decreasing the power consumption of an electrolyzer.
Nowadays, the main and most developed technologies, as far as electrolyzers are concerned, are Proton Exchange Membrane (PEM) technology and alkaline technology.
PEM technology is comprised of a solid electrolyte and has rapid operating dynamics, though there are no current devices with a lot of power. Generally, they tend to be around tens of kilowatts.
Alkaline technology consists of an electrolyte, normally, diluted KOH, that has slower dynamics than PEM technology, but there are more powerful electrolyzers with this technology. They can even produce up to megawatts.
These technologies have been tested in different projects, such as the one led by NREL “Renewable Electrolysis Integrated System Development and Testing” and the one led by IEA “Solar-Wasserstoff-Bayern Hydrogen Demonstration Project”.
Notwithstanding, none of these techniques is adequate, in itself, in order to be combined with wind energy installations. The cause of this problem is that wind has very rapid dynamics and thus, the generated wind power also has said rapid dynamics.
Besides, taking into account that the energy of a wind farm is typically several tens of megawatts, providing electrolyzers of a single technology would not meet the requirements of the system as far as the required power and dynamics are concerned.
On the other hand, more and more attention is being paid recently to issues connected with energy production, such as energy dependence on fossil fuels, gas emissions coming from the greenhouse effect, environmental pollution, impact on climatic change, and, stated briefly, the sustainability of the existing energy systems.
In this context, renewable energies have become the key factor, since they provide society with energy to meets its needs upon using renewable, sustainable and non-polluting sources as the primary energy.
The disadvantage of these technologies generating electricity from renewable sources with respect to traditional technologies, is the variability in the availability of the renewable energy resource, namely wind or solar energy. Therefore, the management capacity of said energy is limited.
Currently, as a result of these limitations, electricity network operators are imposing restrictions on the introduction of new renewable energy generating plants, such as wind farms or photovoltaic power plants.
In order to avoid these restrictions and to get the renewable electricity generation plants to penetrate into the grid system, it is necessary to provide solutions that make it possible to make these sources of energy more manageable.
A novel system for producing electricity and hydrogen is presented as a solution to these above-described problems.
The present invention includes a hybrid device of different electrolysis technologies with different dynamic responses that allow absorbing the fluctuations of the generated electric power due to the variability of the wind source, to be absorbed. The fluctuations of the electric power injected to the electricity network are reduced and/or eliminated.
Another advantage of the invention is that by means of the use of electrolyzers of different technologies, the needs of the system are covered as far as the required power and dynamics are concerned.
Besides, the overall process is improved since there are several electrolyzer technologies that provide different characteristics that can be used as required. An additional advantage of the use of the hybrid electrolyzer device with different dynamics is that the electrolyzers can function as loads of a different power range in each moment and with different dynamics. Thus, they can be used to regulate the output power of the wind farm or wind turbine in particular.
Another advantage is that the use of two electrolyzer technologies with different response dynamics and power capacity permits the control of the frequency of the electric system. The rapid dynamic technology acts as a controlled primary power reserve (in the range of seconds) and the slow dynamic technology acts as a controlled secondary power reserve (in the range of minutes).
Due to the use of two different electrolysis technologies, with different response dynamics and power capacity, it is possible to adapt the electric power, which is injected to the electricity network, to the plant management requirements indicated by the electric system operator, such as the active power reserve, reactive power adjustment, voltage dip control, as well as primary and secondary regulation power control.
Therefore, an invention that makes it possible to solve the problems derived from the variability of the wind source is disclosed. It considerably increases the management capacity of the wind farm, in such a way that it permits it to operate in a way similar to that of conventional power generation stations, meeting all the requirements of the electricity network operators. Besides, in this way, a contribution is achieved to increasing the penetration of renewable energies in the electricity network.